The aim of this proposal is to investigate the effect of neoplasia on the biological and chemical properties of histocompatibility antigens (H-2 and Ia) present in mouse serum. A concerted effort will be made to assess any correlation between the progress of leukemia and mammary carcinoma and quantitative and qualitative changes of soluble histocompatibility antigens in serum. Since our data indicate the presence of H-2 antigens in serum, an effort will be made to determine the concomitant presence of Ia antigens. Attempts will be made to assess the capacity of these antigens to elicit humoral and cellular immune responses in order to evaluate the effect of malignant transformation on the biological profile of these cell suface markers. New methods will be developed for the isolation and purification of Ia and H-2 antigens from the sera of both normal and tumor-bearing mice which will permit the elucidation of their respective molecular structures, in particular their association with beta2-micro-globulin. Xenoantibodies to histocompatibility antigens isolated from mouse serum will be utilized to develop sensitive radioimmunoassays for the detection of Ia and H-2 antigens in serum. Such assays will further facilitate the assessment of quantitative differences of histocompatibility antigens in the sera of normal and tumor-bearing mice. A study of qualitative and quantitative changes in the serum of mice during the progress of neoplastic disease should provide some insight into the pathogenesis of neoplasia and provide a model for the study of human neoplasms.